1. Field of the Invention
The present invention relates generally to field construction apparatus, and more particularly but not by way of limitation, to a method and planer type road construction apparatus that affords precision planing of existing paved roadways.
2. Description of the Prior Art
The planing of roadways or the like involves the use of heavy duty cutting devices that remove a selected top portion of a concrete or bituminous surface. Planing provides an alternative to the usual practice of continued buildup of bituminous layers over a roadway in a resurfacing program of maintenance and repair. As is well known in the art, when a roadway has received a number of resurfacing bituminous layers, there comes a time that the roadway can no longer be simply resurfaced, and the accumulation of layers of bituminous material must be torn out and the roadway is in essence constructed anew. This buildup of bituminous layers is prevented if the to surface of the old roadway is partially removed so that the freshly laid bituminous surface is applied over a recessed surface.
Prior art planers used in the road construction industry have generally consisted of a planing cutter suspended from the undercarriage of grading equipment or the like. Such prior art planers have found limited usage in a road building program for the reason that the planing process performed thereby was generally inaccurate and relatively slow. In an attempt to increase the rate of planing bituminous surfaces, several prior art devices have used heaters to heat the bituminous roadway just in front of the planer's travel to reduce the force required of the planing cutter. The heaters used in the technique known as hot planing usually were fueled by a petroleum product, and were consequently expensive to operate as well as being objectionable due to the production of hydrocarbon vapors and the products of combustion. Also, the roadway serves as a heat sink during hot planing, and it was quickly discovered that an attempt to heat a frozen or very cold bituminous roadway was largely an exercise in futility, leading to the necessity of scheduling hot planing during the warmer seasons of the year. Cold planing, although requiring more cutting power, did not have seasonal limitations.
Furthermore, material removed by the cutting action of prior art planers created considerable problems in cleaning the planed surface, as a large amount of debris was generated and left in the wake of the planar. In cold planing, the planing process literally created a cloud of dust and cuttings, and the whole process was generally very dirty, bothersome and time-consuming.
Perhaps all of the above conditions would have been tolerable and planing would have achieved wider acceptance if accurate surface removal could have been effected, but the results achieved in planing a particular roadway in the past depended very largely upon the skill of the operator. It was also apparent that the greater the depth of cut taken by a pass of a planing cutter, the greater the problem of obtaining a uniform and accurately cut substrate for the next layer of bituminous material. Therefore, it was often necessary to take multiple cutting passes, or to restrict the use of the planing process to those applications which required only shallow cuts.
It is clear from the above that the practice of planing, as applied to the road construction art, has had very limited application. There has not been a way to achieve precision planing for the removal of a selected portion of a roadway to provide a new roadway surface having a predetermined grade and cross slope as is presented by the present invention.